Skepticism: From Pyrrho to Modernity

Introduction

Skepticism is one of the most influential philosophical traditions, which questions the possibility of attaining absolute truth and reliable knowledge. The word “skepticism” comes from the Greek “skepsis,” meaning “inquiry” or “examination.” Unlike dogmatism, which asserts certain truths, skepticism emphasizes the need for suspension of judgment (epoché) in the face of uncertainty. This position does not necessarily lead to nihilism or the complete rejection of knowledge; rather, it encourages continuous inquiry and critical thinking.

The history of skepticism begins in Ancient Greece, specifically with the figure of Pyrrho of Elis, who is considered the founder of Pyrrhonism—the first systematic form of skepticism. From Pyrrho, this tradition evolved across centuries, influencing Academic philosophy, medieval thought, the Enlightenment, and modern epistemology. In this article we will carefully examine the development of skepticism, beginning with its origins in Pyrrho, tracing its key stages and figures, and discussing its influence on the modern world.

Origins: Pyrrho and Early Pyrrhonism

Skepticism as an organized philosophical school arose in the fourth century before the Common Era, thanks to Pyrrho of Elis (approximately 360–270 before the Common Era). Pyrrho left no writings of his own, and our knowledge of his ideas is based on the testimonies of followers such as Timon of Phlius, and later authors, including Sextus Empiricus.

Pyrrho lived in the Hellenistic era, when Greek culture spread across the world through the conquests of Alexander the Great. According to legend, Pyrrho accompanied Alexander on his campaigns in India, where he may have encountered Indian skeptical philosophers or ascetics, such as the Gymnosophists or Buddhists, who emphasized the illusory nature of perception. This journey likely shaped his views: Pyrrho concluded that things in the world are indeterminate and that our sensations and opinions cannot provide reliable knowledge.

The central idea of Pyrrhonism is epoché (suspension of judgment). Pyrrho argued that for any assertion, there exists an equally strong opposing assertion; therefore, the wise person should refrain from making categorical judgments. This leads to ataraxia—a state of inner tranquility, free from the anxieties caused by dogmatic beliefs. Pyrrho illustrated his ideas with anecdotes: for instance, he is said to have walked along the edge of a cliff without fear, trusting that reality is inaccessible to judgment, although his students had to save him from danger.

Timon of Phlius (approximately 320–230 before the Common Era), Pyrrho’s closest disciple, developed these ideas in satirical poems and fragments. He criticized dogmatic philosophers such as Aristotle and Plato for their claims to knowledge. Timon introduced the notion of “phenomena” (appearances), emphasizing that we can describe how things appear to us, but not how they truly are.

Early Pyrrhonism was more a way of life than a strict doctrine. It stood in contrast to Stoicism and Epicureanism, which offered paths to happiness through knowledge and ethics. The Pyrrhonists saw skepticism as a tool for achieving inner harmony.

Academic Skepticism: From Arcesilaus to Carneades

After Pyrrho, skepticism evolved within Plato’s Academy, where it became known as “Academic Skepticism.” This branch differed from Pyrrhonism by being more focused on dialectic and the critique of other schools.

Arcesilaus (approximately 316–241 before the Common Era), head of the Middle Academy, introduced skepticism into the Platonic tradition. He interpreted Plato as a skeptic, highlighting the aporia (perplexity) in the dialogues. Arcesilaus attacked the Stoics, especially their theory of the “cataleptic impression”—the claim that some perceptions give indubitable knowledge. He argued that all impressions are subjective and may be false, therefore suspension of judgment is necessary.

Carneades (approximately 214–129 before the Common Era), leader of the New Academy, developed these ideas further. In 155 before the Common Era he visited Rome as an ambassador and caused a sensation with his lectures: on one day he defended the concept of justice, and on the next day he refuted it, demonstrating the equal strength of arguments on both sides. Carneades introduced the concept of the “probable,” suggesting that while absolute knowledge is impossible, we may act on the basis of probable judgments. This made Academic Skepticism more practical, influencing Roman thought.

Other figures, such as Clitomachus and Philo of Larissa, continued this tradition, softening its radicalism into a form of probabilism (a probabilistic approach).

The Roman Period and Sextus Empiricus

In the Roman era Pyrrhonism was revived by Aenesidemus (first century before the Common Era), who systematized the “tropes”—arguments for skepticism. He identified ten tropes showing how perception depends on the subject, the object, circumstances, and so forth. For example, one trope concerns differences between animals: what is pleasant to a human being may be harmful to another creature.

Agrippa (first century of the Common Era) added five more tropes, including infinite regress (every argument requires justification, which in turn requires further justification) and circular reasoning.

The most complete source on ancient skepticism is Sextus Empiricus (second–third century of the Common Era), a physician and philosopher. In his works, such as Outlines of Pyrrhonism and Against the Dogmatists, he presented Pyrrhonism as a therapy against dogmatism. Sextus distinguished Pyrrhonists (skeptics) from dogmatists and Academics, stressing that the true skeptic does not even assert the impossibility of knowledge—that itself would be dogma. His works survived and became the foundation for the revival of skepticism in Europe.

The Middle Ages and the Renaissance: The Rediscovery of Skepticism

In the Middle Ages skepticism was marginalized because of the dominance of Christian dogmatism, but elements of it entered through Augustine of Hippo, who used skeptical arguments against the Manicheans.

The revival came in the sixteenth century with the publication of the works of Sextus Empiricus. Michel de Montaigne (1533–1592), in his Essays, popularized Pyrrhonism, using it to criticize religious fanaticism during the wars in France. Montaigne became famous for the phrase “Que sais-je?” (“What do I know?”), highlighting the modesty of knowledge.

This influenced both the Reformation and the Counter-Reformation, where skepticism was employed to undermine authorities.

The Early Modern Period: Descartes, Hume, and Kant

In the seventeenth century René Descartes (1596–1650) applied “methodical skepticism” in his Meditations on First Philosophy. He doubted everything—sensations, mathematics, even the existence of God—in order to find an indubitable foundation. That foundation became “Cogito, ergo sum” (“I think, therefore I exist”): the very act of doubting proves the existence of the one who doubts. Descartes turned skepticism into the starting point for building his own rationalist system.

David Hume (1711–1776) developed empirical skepticism in his Treatise of Human Nature. He showed that causality is not an objective reality but a habit of the mind, and he questioned induction, which had a profound influence on the philosophy of science.

Immanuel Kant (1724–1804) responded to Humean skepticism in his Critique of Pure Reason, distinguishing between phenomena (appearances) and noumena (things-in-themselves), which are inaccessible to knowledge.

Modern Skepticism: Epistemology and New Dogmas

In the twentieth and twenty-first centuries skepticism was fully expressed in the language of the philosophy of knowledge. If for Pyrrho epoché was a way of life, and for Carneades a dialectical technique, now this impulse found institutional continuation in epistemology (epistēmē meaning “knowledge,” logos meaning “study”). Epistemology is systematized skepticism: it raises the same questions as the ancient skeptics, but in a new form. What can be considered knowledge? How do we distinguish justified belief from opinion? Where is the boundary between certainty and probability?

Karl Popper established the principle of fallibilism: all knowledge remains a hypothesis that may be falsified, but never finally confirmed. Skepticism ceased to be merely the suspension of judgment and became the working mode of science: models survive only as long as they withstand criticism.

Skepticism remains alive and relevant. It reminds us that knowledge is never given once and for all: it must continually be rediscovered—through doubt, inquiry, and the willingness to reconsider even the most familiar frameworks.

Conclusion

Skepticism, which began with Pyrrho as a path to tranquility through doubt, has become a powerful tool for critique and inquiry. From the ancient tropes to modern debates, it reminds us of the limits of human cognition. In an age of information overload, skepticism is as urgent as ever: it teaches us not to believe blindly, but to investigate. As Montaigne said, true wisdom lies in the acknowledgment of one’s own ignorance.